Isn't modern technology grand? See also pasteurization, canning, pickling, and many many other technologies that help food last longer. Why should people care what something is "supposed to" do? Many kinds of food are "supposed to" spoil quickly, but we've gone to great lengths to overcome that.

(For clarity in case there is a nomenclature difference here, UHT milk is shelf-stable liquid milk that's entirely equivalent to any milk but lasts much longer before expiring. That's separate from things like evaporated milk or powdered milk, which are also substitutes for milk but not directly equivalent.)